Sternum - Anatomy Pictures and Information Home > Skeletal System > Bones of the Chest and Upper Back > Sternum Sternum The sternum, commonly known as the breastbone, is a long, narrow flat bone that serves as the keystone of the rib cage and stabilizes the thoracic skeleton. Several muscles that move the arms, head, and neck have their origins on the sternum. It also protects several vital organs of the chest, such as the heart, aorta, vena cava, and thymus gland that are located just deep to the sternum. The sternum is located along the body’s midline in the anterior thoracic region just deep to the skin. It is a flat bone about six inches in length, around an inch wide, and only a fraction of an inch thick.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Sternum Description [Continued from above] . . .

The sternum develops as three distinct parts: the manubrium, the body of the sternum (sometimes called the gladiolus), and the xiphoid process. The shape of the sternum looks somewhat like a sword pointing downwards, with the manubrium forming the handle, the body forming the blade, and the xiphoid process forming the tip. In fact, the name manubrium means “handle,” gladiolus means “sword,” and xiphoid means “sword-shaped.” The manubrium is the widest and most superior region of the sternum. It forms joints with the clavicles and the first and second pairs of ribs through their costal cartilages. The clavicles meet the manubrium at the concave clavicular notches to form the sternoclavicular joint, the only point of skeletal attachment between the pectoral girdle of the shoulder and the axial skeleton of the thorax. Slight indentations on the lateral sides of the manubrium provide attachment points for the costal cartilages of the ribs. At its inferior end, the manubrium meets the body of the sternum at the joint with the costal cartilage of the second ribs.

Here it forms the sternal angle, a slight posterior bend in the sternum that can be felt through the skin and serves as an important anatomical landmark in the medical profession. Several important muscles attach via tendons to the manubrium, including the sternocleidomastoid, pectoralis major, sternohyoid, and sternothyroid muscles. The body of the sternum is the longest region of the sternum and is roughly rectangular in shape. The costal cartilages of the second through tenth ribs connect to the body of the sternum to form the bulk of the rib cage. Just like in the manubrium, slight concave indentations in the lateral sides of the body of the sternum provide stronger attachment points for the costal cartilages to prevent rib separation. In addition, the powerful pectoralis major muscles that adduct and flex the humerus at the shoulder attach to the anterior surface of the body of the sternum and manubrium. The smallest and most inferior region of the sternum, the xiphoid process, begins life as a region of flexible hyaline cartilage attached to the end of the body of the sternum.

The xiphoid process slowly ossifies throughout childhood and adulthood until around age 40 when all of its cartilage is replaced by bone. Regardless of its degree of ossification, the xiphoid process serves as an important attachment point for the tendons of the diaphragm, rectus abdominis, and transverse abdominis muscles. Several undesired events can take place at the sternum. During open heart surgery, the sternum must be cut in half along its long axis to provide access to the heart. After surgery, the two halves of the sternum must be wired back together with stainless steel wire to prevent their separation. Any extreme stresses placed on the broken sternum after surgery, such as lifting heavy objects, can result in the wires cutting through the bony tissue and severely damaging the sternum. Another risk associated with the sternum is the fracturing of the xiphoid process during CPR, which can potentially lead to the xiphoid process breaking off and lodging into one of the delicate vital organs below it.

Prepared by Tim Taylor, Anatomy and Physiology Instructor Sternum | Chest bone Sternum | Chest bone It consists of three parts; Manubrium sterni: The uppermost part Body (shaft): The middle part Xiphoid process: The lowest part Ossification of sternum: Ossification occurs by a total of 6 centers. One is for manubrium, four for body and one for xiphoid process. Sternal angle: It is the angle formed between the manubrium and body of sternum. The vertex of this angle lies at the manubriosternal joint. Anatomy of Sternum: Sternum | Chest bone The sternum (chest bone) lies in the midline of the anterior chest wall. It is a flat bone that can be divided into three different parts: Manubrium sterni, Body of sternum and Xiphoid process. Manubrium: It is the upper-most part of the sternum that articulates with: The right and left clavicles First costal cartilages of both sides Upper part of the second costal cartilage of both sides It is quadrangular in form and lies at the level of third and fourth thoracic vertebrae of the spinal cord.

The superior border of manubrium is thick, actually the thickest part of the bone and forms the jugular notch. On the surface of human body, the jugular notch can be easily seen as depression just above the manubrium. The anterior surface of this part of the bone is convex from side to side while the posterior surface is concave. Body of sternum: It is longer, narrower and thinner as compared to the manubrium sterni, with which it articulates superiorly at the manubriosternal joint, which is of fibrocartilaginous type. At the lower border, it articulates with the xiphoid process at the xiphisternal joint. The body of sternum is of flat contours and contains notches on each side for articulation with the costal cartilages. There are a total of 12 costal cartilages but only first 7 articulate with the sternum directly. Xiphoid process: It is the smallest and lowest part of the bone and is actually a thin plate of hyaline cartilage. It may become ossified at its proximal end in the adult life but it is purely cartilaginous in children and teenagers.

It is not attached to ribs or costal cartilages. Ossification of Sternum: Ossification of sternum The sternum originally consists of two cartilaginous bars, situated one on either side of the median plane and connected with the cartilages of the upper ribs. These two bars fuse with each other along the middle line to form the cartilaginous sternum which is ossified from six centers: One for manubrium sterni: Appears at the sixth month and rarely unites with other centers except at the old age. Four for the body: The first of these four appears at sixth month, second and third at 7th month and fourth appears one year after birth. They unite with each other after puberty. One for the xiphoid process: It appears at 5th to 18th year of life but remains partly cartilaginous. Sternal Angle Sternal Angle: It is also known as Angle of Louis and is formed by the articulation of the body of sternum with the manubrium sterni. It is present in the form of ridge at the site of the manubriosternal joint and lies opposite the intervertebral disc between third and fourth thoracic vertebrae.

The sterna angle lies adjacent to the second intercostals space fairly consistently and for this reason, it is used as a guide to count the ribs and intercostals spaces. Share this page: Sternum | definition of sternum by Medical dictionary Sternum | definition of sternum by Medical dictionary sternum [ster´num] a plate of bone forming the middle of the anterior wall of the thorax and articulating with the clavicles and the cartilages of the first seven ribs. It consists of three parts, the manubrium, the body, and the xiphoid process. From Dorland's, 2000. ster·na (ster'nŭm, -nī, -nă), [TA] A long flat bone, articulating with the cartilages of the first seven ribs and with the clavicle, forming the middle part of the anterior wall of the thorax; it consists of three portions: the corpus or body, the manubrium, and the xiphoid process. [Mod. L. fr. G.

sternon, the chest] sternum /ster·num/ (ster´num) [L.] a longitudinal unpaired plate of bone forming the middle of the anterior wall of the thorax, articulating above with the clavicles and along its sides with the cartilages of the first seven ribs. Its three parts are the manubrium, body, and xiphoid process. sternum (stûr′nəm) n. pl. ster·nums or ster·na (-nə) 1. A long flat bone in most vertebrates that is situated along the ventral midline of the thorax and articulates with the ribs. The manubrium of the sternum articulates with the clavicles in humans and certain other vertebrates. Also called breastbone. 2. The ventral portion of a body segment of an arthropod. sternum [stur′nəm] Etymology: Gk, sternon the elongated flattened bone forming the middle part of the thorax. It supports the clavicles; articulates directly with the first seven pairs of ribs; and comprises the manubrium, the gladiolus (body), and the xiphoid process.

It is composed of highly vascular tissue covered by a thin layer of bone. Sternum ster·num , pl. sterna (stĕr'nŭm, -nă) [TA] A long, flat bone, articulating with the cartilages of the first seven ribs and with the clavicle, which forms the middle part of the anterior wall of the thorax; it consists of three portions: the corpus or body, the manubrium, and the xiphoid process. [Mod. L. fr. G. sternon, the chest] sternum (stĕr′nŭm) [L.] STERNUM The narrow, flat bone in the median line of the thorax in front. It consists of three portions: the manubrium, the body or gladiolus, and the ensiform or xiphoid process. See: illustration cleft sternum A congenital fissure of the sternum. sternum The breastbone. sternum the breastbone that occurs in the ventral region of the chest and to which, in flying birds where the bone is keel-shaped, are attached the pectoral muscles associated with flight.

Anteriorly it is connected to the shoulder girdle, and the ventral ends of the ribs are attached along its length. Sternum Also referred to as the breast bone, this is the long flat bone in the middle of the chest. ster·num , pl. sterna (stĕr'nŭm, -nă) [TA] A long, flat bone, articulating with the cartilages of the first seven ribs and with the clavicle, which forms the middle part of the anterior wall of the thorax. [Mod. L. fr. G. sternon, the chest] sternum, n the elongated, flattened bone forming the middle portion of the thorax. It supports the clavicles and articulates directly with the first seven pairs of ribs. sternum the breastbone, a median segmented skeletal structure made up of several elements or sternebrae, often with a considerable portion remaining cartilaginous into adulthood. It articulates with the cartilages of the sternal ribs and clavicles when large.

It has three parts, the manubrium, the body and the xiphoid process, and consists of vascular, spongy bone covered with a thin layer of compact bone. In ruminants it has a flat ventral surface, while in horses it bears a keel (carina). It is especially well developed, as a nonsegmented keeled bone, in flying birds. inherited short sternum in the North Country Cheviot breed; characterized by a heavy mortality in newborn lambs resulting from rupture of the liver; the latter thought to occur because of the exposed position of the liver as a result of the absence of the sternum. Chapter 19: The skeleton of the thorax Figure legends Chapter 19: The skeleton of the thorax The skeleton of the thorax includes the sternum, ribs and costal cartilages, and thoracic vertebrae and intervertebral discs (fig. 19-1 ). Sternum The sternum, or breast bone, is a flat bone that, from superior to inferior, consists of three parts: manubrium, body, and xiphoid process (figs. 19-1 and 19-2 ).

It is useful to remember that the manubrium and body are approximately on the level of thoracic vertebrae 3-4 and 5 to 10, respectively (see figs. 20-8 and 21-1 ). Its subcutaneous location and the thinness of its compacta have made the sternum a common site for puncture by a needle to obtain marrow for study. The upper border of the manubrium is marked by the jugular notch, which is easily palpable and is usually at the level of the T3 vertebrae. On each side of this is a notch for the medial end of the clavicle. The first costal cartilage is attached to the side of the manubrium. Below, the manubrium articulates with the body of the sternum at the sternal angle, which is marked by a palpable (and sometimes visible) transverse ridge about 5 cm below the jugular notch. The sternal angle is an important bony landmark at the T4 or 5 vertebral level. It indicates not only the manubriosternal junction but also the level of the second costal cartilages; hence it is a reference point in counting ribs.

Rarely, however, the sternal angle is at the level of the third costal cartilages. The manubriosternal junction (i.e., the union of the manubrium with the body of the sternum) is usually fibrocartilaginous, but it may become ossified. The body of the sternum, about twice as long as the manubrium, is notched on each side to receive costal cartilages 2 to 7. Transverse ridges may indicate its development from several pieces. The xiphosternal joint (i.e., the union of the body of the sternum with the xiphoid process) is usually fibrocartilaginous, but it too may become ossified. It is at the apex of the infrasternal angle and is usually at the level of thoracic vertebra 10 or 11. The xiphoid process is a small and variable piece of hyaline cartilage that contains a bony core. It lies in the epigastric fossa, or "pit of the stomach." The sternum develops bilaterally in the embryo, and it later ossifies from a variable number of bilateral and median centers.

Ribs There are usually 12 ribs on each side of the body (fig. 19-3 ). They are elongated yet flattened bones that curve inferior and anterior from the thoracic vertebrae. The ribs, as well as the costal cartilages, increase in length from the first to the seventh, and their obliquity increases from the first to the ninth. Generally, ribs 1 to 7 are connected to the sternum' by their costal cartilages and are called true ribs, whereas ribs 8 to 12 are termed false ribs. Usually, ribs 8 to 10, by means of their costal cartilages, join the costal cartilage immediately above, whereas ribs 11 and 12, which are free, are known as floating ribs. A supernumerary rib may be found in either the cervical or lumbar region. In thoracic surgery, a portion of a rib can be excised, leaving its periosteum, which later allows regeneration of the bone. Ribs 3 to 9. Ribs 3 to 9 have certain features in common and are known as typical ribs (figs. 19-4 and 19-5 ).

Each has a head, neck, and shaft. The head presents two articular surface: one for the corresponding vertebral body and one for the vertebra immediately superior. The junction of the neck and shaft is marked by a tubercle, which articulates with the transverse process of the corresponding vertebra. The shaft, which is curved and twisted, presents an angle posteriorly, which indicates the lateral extent of the erector spinae and is the weakest part of the rib. The curvature of the rib is such that a person lying on his back is supported by the spinous processes and the angles of the ribs. The concave, inner surface of the shaft is marked inferiorly by the costal groove, which gives attachment to the internal intercostal muscle and shelter to the intercostal vein, artery, and nerve (from superior to inferior). The ribs ossify from a primary center for the shaft and secondary centers for the head and tubercle. The first rib. The first rib (fig. 19-6 ) is short and forms part of the thoracic inlet. The head articulates with the T1 vertebra, and the neck lies behind the apex of the lung.

The flat upper surface faces superiorly and may present a groove for the subclavian artery and the lower trunk of the brachial plexus, anterior to which is the tubercle for the scalenus anterior muscle. Further anteriorly is a shallow groove for the subclavian vein. The first rib is difficult to palpate in vivo, but the first intercostal space can be identified immediately below the clavicle. The second rib, which is much longer than the first, is curved but not twisted. It articulates with T1 and 2 vertebral bodies and presents a tuberosity for the serratus anterior muscle. Ribs 10 to 12. Rib 10 usually articulates with the tenth thoracic vertebrae, only. Rib 11, which articulates only with the T11 vertebrae, has an indistinct tubercle, angle, and costal groove. Rib 12, which articulates with the T12 vertebra, is small, slender, and variable in length. The differences in length have to be kept in mind in surgical approaches to the kidney.

The costal cartilages are comprised of hyaline cartilage, which later may become ossified. They fit into depressions in the anterior ends of the ribs, and the upper seven or eight articulate with the sternum. The costal cartilages impart resiliency to the chest wall. They often become partly ossified later in life. Thoracic vertebrae (figs. 39-5 , 39-6 and 39-7 ) The thoracic vertebrae are described with the back. The superior costal facet of a typical thoracic vertebra, together with the intervertebral disc and the inferior costal facet of the vertebra immediately superior, forms a socket for the head of the corresponding rib. Questions 19-1 What is the vertebral level of the manubrium sterni? 19-1 The manubrium is approximately on the level of thoracic vertebrae 3 and 4. A horizontal section between these vertebrae would pass through the great vessels of the neck, the trachea, esophagus, and upper part of the lungs.

A horizontal section through the lower end of the sternum (approximately T10 vertebral level) would be expected to pass through the lower part of the heart and lungs but might easily include a portion of the right lobe of the liver. Thus pericardial, pleural, and peritoneal cavities might be opened in one section. 19-2 What lies on the upper surface of the first rib? 19-2 The subclavian vein (anterior to the anterior scalene muscle) and the subclavian artery and lower trunk of the brachial plexus (posterior to the anterior scalene muscle) lie on the upper surface of the first rib. If a cervical rib is present, angulation of the subclavian artery, brachial plexus, or both over such a rib may cause such features as pain on movement of the arm and numbness of the fingers. This is one example of the "neurovascular compression syndrome" of the upper limb. 19-3 How are ribs counted? 19-3 Ribs are counted from above down, beginning with the second, which is generally (but not always) opposite the sternal angle.

The first ribs are concealed by the clavicles. Figure legends Figure 19-1 The bones of the thorax. Note that the upper two and a half and the lower two and a half thoracic vertebrae are visible. Figure 19-2 The sternum and its muscular attachments. Figure 19-3 Photograph of the ribs. Figure 19-4 The internal aspect of the right seventh rib. Note the slope inferior and anterior and the twist of the shaft. Figure 19-5 The right seventh rib from inferior and posterior. Figure 19-6 The superior surface of the first rib, showing grooves for vessels as well as muscular and ligamentous attachments. The scalenus minimus (not shown) is also inserted into the first rib. Jump to: Sternum - Anatomy, Fracture, Pain and Location Sternum Treatment for Sternum pain Sternum Definition and Function The sternum or breastbone is a vertical flat bone lying at the anterior middle part of the chest. Externally, it is made up of compact bone. Inside of it is a cancellous or spongy tissue that is entirely vascular. The adult length of the sternum measures 15-17 cm.

It is larger in males than in females. Sternum protects the organs inside the mediastinum, especially the heart [1, 2, 3]. Parts of the Sternum Manubrium The manubrium sterni is the most superior part of the sternum that lies at the levels of 3rd and 4th thoracic vertebrae. The superior border of the manubrium has the broadest structure among the other parts of the sternum. On its center is the suprasternal or presternal or jugular notch. This is the depressed part that can be palpated in between the clavicles. The lateral sides of the superior border of the sternum articulate with the clavicles via sternoclavicular joints. The lateral borders have facets that articulate with the ribs. The inferior border has a cartilage that articulates with the sternal body at manubriosternal joint. The anterior surface serves as an attachment to the pectoralis major and sternocleidomastoid muscles. The posterior surface serves as an attachment to the sternohyoid and sternothyroid muscles.

Body The corpus sterni or gladiolus is the longest part of the sternum, although it is narrower than the manubrium. The body of the sternum is found at the level of T5-T9 vertebrae. The anterior surface of the sternal body is almost flat. It is where the pectoralis major is attached. There are three horizontal ridges that pass through the 3rd, 4th, and 5th articular facets. Between the 3rd and 4th parts of the sternal body, the sternal foramen can be seen. The posterior surface also has these three lines. On its lower end is the origin of the transversus thoracis. The superior border of the sternum articulates with the manubrium through the manubriosternal joint. The gap between the two is called the sternal angle or angulus Ludovici or angle of Louis, named after Antoine Louis. The lateral border has articular depressions on which the 2nd to 7th costal cartilages are attached.

The inferior border is the narrowest part of the manubrium and it articulates with the xiphoid process through the xiphisternal joint which lies at the level of the 9th thoracic vertebra. At birth until young adulthood, there are four sternebrae attached to sternal synchondroses. When a person reaches 25 years, these sternebrae fuse to form three synostoses. Xiphoid Process The xiphoid process, also known as processus xiphoideus, ensiform or xiphoid appendix, is the smallest part of the sternum. It lies at the level of T10 vertebra. Costal cartilages nor ribs are attached to it. It is made up of cartilage until it ossifies at the age of 40 and in some cases, they become one with the sternal body in old age. The superior border articulates with the sternal body via xiphisternal joint. On its sides are articular facets that provide attachment to the 7th rib. The inferior border gives rise to the linea alba. The anterior surface is where the anterior costoxiphoid ligament and a part of rectus abdominis are attached.

The posterior costoxiphoid ligament, transversus thoracis, and diaphragm are attached to the posterior surface. The lateral borders are connected with abdominal aponeuroses [1, 2, 4]. For more information : please check – Xiphoid Process Pain Anatomy Images: Where is the Sternum Located? Picture 1: Sternum is a part of the skeletal system. It lies on the anterior thoracic wall in the middle. Its parts are the manubrium (green), body (blue), and xiphoid process (violet). Image Source: wikipedia.org Picture 2: Sternum, Costal Cartilages, and Ribs Image Source: newhealthguide.org Picture 3: Anterior View of the Thoracic Cage Image Source: antranik.org Picture 4: Anterior and Lateral Views of the Sternum Image Source: paradoja7.com Picture 5: Anterior View of the Sternum Image Source: oxford174.com Image Source: Clinical Anatomy 2nd edition Picture 7: The first sternocostal joint is categorized as synchondrosis. The succeeding joints are symphysis.

Image Source: faculty.ucc.edu Picture 8: Joints of the Sternum Image Source: healthguidance.org Picture 9: Posterior Surface of the Sternum and Articulations with the Costal Cartilages Image Source: wikipedia.org Clinical Importance of Sternum Sternal Angle or Angle of Louis as a Landmark Sternal angle or the angle of Louis is the articulation that is formed by the fusion of manubrium and body of the sternum. This is a very important landmark since it is where the costal cartilages and ribs are first counted. It rests at the level of 2nd costal cartilage and in between 4th and 5th thoracic vertebrae. Xiphoid Process as a Landmark Xiphoid process may be small but it is an important landmark for the structures beneath it. It serves as a landmark for: The anatomical end for anterior thoracic cage Formation of infrasternal or subcostal angle together with the subcostal margins Inferior border of the heart Superior border of the liver Diaphragm’s central tendon Bone Marrow Biopsy The sternum is a hematopoietic tissue, meaning blood cells are produced in this site.

To obtain a bone marrow biopsy, a large bore needle is introduced into the sternum and a sample is aspirated [4]. Surgery A bone saw is used to gain access to the thoracic cavity in surgeries involving the heart, great vessels, thymus gland, and retrosternal goiter. Wire sutures are used to close the sternum in surgery. Sternal Fracture The costal cartilages cushion the sternum and protect it from injury or trauma. However, too much force cannot be handled by the sternum and that is where fracture and dislocation set in. If the rescuer’s hands are placed wrongly on the chest of the patient during cardiopulmonary resuscitation (CPR), the xiphoid process might be fractured and pierce the underlying organs. There may be a sensation of a “popping” sternum in sternal fracture. The manubrium may be displaced from the sternal body. Fracture of the sternum may also be associated with fracture of the thoracic vertebrae [3, 5]. Sternum Pain Picture 10: Thoracic Cage Injuries Sternal fracture is a form of a simple thoracic cage injury.

Although simple, it should still be given immediate medical attention. Image Source: Netter’s Clinical Anatomy 2nd edition, Saunders, 2010 Causes of Sternum pain Fractures, dislocations, joint separations, wounds, or any other forms of injury or trauma to the thoracic cage cause pain to the sternum. Sternum is located in the middle of the chest cavity. The surrounding anatomical structures are attached to it. So if these become damaged, no matter how simple the diagnosis may be, there will be a resulting sternal pain. Respiration is an involuntary, essential function. It involves spontaneous, continuous movement of the thoracic cage, including the sternum. If the sternum is broken, common sense will tell that pain results. There will be pain in your sternum with each breath you take. Also see : Causes of Pain under right rib cage Treatment for Sternum pain To deal with sternum pain, nerve block is performed wherein the intercostal nerve that transmits pain signals to the brain is being anesthetized [6].

Gray H, Anatomy of the Human Body, Bartleby Bookstore Moore KL et al, Clinically Oriented Anatomy 6th edition, Lippincott Williams & Wilkins 2010, pp 76-78 Tortora GJ & Derrickson B, Principles of Anatomy & Physiology 13th edition, Biological Science Textbooks Inc. 2012, p 245 Snell RS, Clinical Anatomy by Regions 9th edition, Lippincott Williams & Wilkins 2012, p 35 Ellis H, Clinical Anatomy 11th edition, Blackwell Publishing 2006, p 11 Hansen JT, Netter’s Clinical Anatomy 2nd edition, Saunders 2010, p 76 Related posts: II. Osteology. 4a. The Sternum. Gray, Henry. 1918. Anatomy of the Human Body. FIG. 115 Anterior surface of sternum and costa cartilages. ( See enlarged image ) The sternum (Figs.

115 to 117) is an elongated, flattened bone, forming the middle portion of the anterior wall of the thorax. Its upper end supports the clavicles, and its margins articulate with the cartilages of the first seven pairs of ribs. It consists of three parts, named from above downward, the manubrium, the body or gladiolus, and the xiphoid process; in early life the body consists of four segments or sternebr. In its natural position the inclination of the bone is oblique from above, downward and forward. It is slightly convex in front and concave behind; broad above, becoming narrowed at the point where the manubrium joins the body, after which it again widens a little to below the middle of the body, and then narrows to its lower extremity. Its average length in the adult is about 17 cm., and is rather greater in the male than in the female. 2 Manubrium (manubrium sterni).The manubrium is of a somewhat quadrangular form, broad and thick above, narrow below at its junction with the body.

3 Surfaces.Its anterior surface, convex from side to side, concave from above downward, is smooth, and affords attachment on either side to the sternal origins of the Pectoralis major and Sternocleidomastoideus. Sometimes the ridges limiting the attachments of these muscles are very distinct. Its posterior surface, concave and smooth, affords attachment on either side to the Sternohyoideus and Sternothyreoideus. FIG. 116 Posterior surface of sternum. ( See enlarged image ) FIG. 117 Lateral border of sternum. ( See enlarged image ) Borders.The superior border is the thickest and presents at its center the jugular or presternal notch; on either side of the notch is an oval articular surface, directed upward, backward, and lateralward, for articulation with the sternal end of the clavicle. The inferior border, oval and rough, is covered in a fresh state with a thin layer of cartilage, for articulation with the body.

The lateral borders are each marked above by a depression for the first costal cartilage, and below by a small facet, which, with a similar facet on the upper angle of the body, forms a notch for the reception of the costal cartilage of the second rib. Between the depression for the first costal cartilage and the demi-facet for the second is a narrow, curved edge, which slopes from above downward and medialward. 5 Body (corpus sterni; gladiolus).The body, considerably longer, narrower, and thinner than the manubrium, attains its greatest breadth close to the lower end. 6 Surfaces.Its anterior surface is nearly flat, directed upward and forward, and marked by three transverse ridges which cross the bone opposite the third, fourth, and fifth articular depressions. 18 It affords attachment on either side to the sternal origin of the Pectoralis major. At the junction of the third and fourth pieces of the body is occasionally seen an orifice, the sternal foramen, of varying size and form.

The posterior surface, slightly concave, is also marked by three transverse lines, less distinct, however, than those in front; from its lower part, on either side, the Transversus thoracis takes origin. 7 Borders.The superior border is oval and articulates with the manubrium, the junction of the two forming the sternal angle (angulus Ludovici 19 ). The inferior border is narrow, and articulates with the xiphoid process. Each lateral border (Fig. 117) , at its superior angle, has a small facet, which with a similar facet on the manubrium, forms a cavity for the cartilage of the second rib; below this are four angular depressions which receive the cartilages of the third, fourth, fifth, and sixth ribs, while the inferior angle has a small facet, which, with a corresponding one on the xiphoid process, forms a notch for the cartilage of the seventh rib. These articular depressions are separated by a series of curved interarticular intervals, which diminish in length from above downward, and correspond to the intercostal spaces.

Most of the cartilages belonging to the true ribs, as will be seen from the foregoing description, articulate with the sternum at the lines of junction of its primitive component segments. This is well seen in many of the lower animals, where the parts of the bone remain ununited longer than in man. 8 Xiphoid Process (processus xiphoideus; ensiform or xiphoid appendix).The xiphoid process is the smallest of the three pieces: it is thin and elongated, cartilaginous in structure in youth, but more or less ossified at its upper part in the adult. 9 Surfaces.Its anterior surface affords attachment on either side to the anterior costoxiphoid ligament and a small part of the Rectus abdominis; its posterior surface, to the posterior costoxiphoid ligament and to some of the fibers of the diaphragm and Transversus thoracis, its lateral borders, to the aponeuroses of the abdominal muscles.

Above, it articulates with the lower end of the body, and on the front of each superior angle presents a facet for part of the cartilage of the seventh rib; below, by its pointed extremity, it gives attachment to the linea alba. The xiphoid process varies much in form; it may be broad and thin, pointed, bifid, perforated, curved, or deflected considerably to one or other side. Structure.The sternum is composed of highly vascular cancellous tissue, covered by a thin layer of compact bone which is thickest in the manubrium between the articular facets for the clavicles. 11 Ossification.The sternum originally consists of two cartilaginous bars, situated one on either side of the median plane and connected with the cartilages of the upper nine ribs of its own side. These two bars fuse with each other along the middle line to form the cartilaginous sternum which is ossified from six centers: one for the manubrium, four for the body, and one for the xiphoid process (Fig. 118) .

The ossific centers appear in the intervals between the articular depressions for the costal cartilages, in the following order: in the manubrium and first piece of the body, during the sixth month; in the second and third pieces of the body, during the seventh month of fetal life; in its fourth piece, during the first year after birth; and in the xiphoid process, between the fifth and eighteenth years. The centers make their appearance at the upper parts of the segments, and proceed gradually downward. 20 To these may be added the occasional existence of two small episternal centers, which make their appearance one on either side of the jugular notch; they are probably vestiges of the episternal bone of the monotremata and lizards. Occasionally some of the segments are formed from more than one center, the number and position of which vary (Fig. 120) . Thus, the first piece may have two, three, or even six centers.

When two are present, they are generally situated one above the other, the upper being the larger; the second piece has seldom more than one; the third, fourth, and fifth pieces are often formed from two centers placed laterally, the irregular union of which explains the rare occurrence of the sternal foramen (Fig. 121) , or of the vertical fissure which occasionally intersects this part of the bone constituting the malformation known as fissura sterni; these conditions are further explained by the manner in which the cartilaginous sternum is formed. More rarely still the upper end of the sternum may be divided by a fissure. Union of the various centers of the body begins about puberty, and proceeds from below upward (Fig. 119) ; by the age of twenty-five they are all united. The xiphoid process may become joined to the body before the age of thirty, but this occurs more frequently after forty; on the other hand, it sometimes remains ununited in old age. In advanced life the manubrium is occasionally joined to the body by bone. When this takes place, however, the bony tissue is generally only superficial, the central portion of the intervening cartilage remaining unossified.

FIG. 118 Ossification of the sternum. ( See enlarged image ) FIG. 119 No caption. ( See enlarged image ) FIG. 120 Peculiarities. ( See enlarged image ) FIG. 121 No caption. ( See enlarged image ) Body of Sternum - Anatomy Pictures and Information Home > Skeletal System > Bones of the Chest and Upper Back > Body of Sternum Body of Sternum The body of the sternum is the middle portion of the sternum, or breastbone, which is a long, narrow, flat plate that forms the center of the front of the chest. It develops in three parts. By middle life, the lower, xiphoid process, of the sternum will fuse to the body of the sternum. The sides of the manubrium and the body are notched where they unite with costal cartilages. Sternum ‹ › Description The sternum (breast bone) is an elongated, flattened bone, forming the middle portion of the anterior wall of the thorax. Its upper end supports the clavicles, and its margins articulate with the cartilages of the first seven pairs of ribs.

It consists of three parts, named from above downward, the manubrium, the body or gladiolus, and thexiphoid process; in early life the body consists of four segments or sternebrœ. In its natural position the inclination of the bone is oblique from above, downward and forward. It is slightly convex in front and concave behind; broad above, becoming narrowed at the point where the manubrium joins the body, after which it again widens a little to below the middle of the body, and then narrows to its lower extremity. Its average length in the adult is about 17 cm., and is rather greater in the male than in the female. This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from Anatomical hierarchy

Question: Which bone in the human body is formed by the manubrium, the body (or gladiolus) and the xiphoid process?
Answer: Sternum